8/13/2019 PV776-20 001146

1/5

Service BulletinVolvo Trucks North America, Inc.Greensboro, NC USA

Date Group No. Pa

12.2003 870 15 1

Trucks

Climate Un

Stepper Motor TestinVN, VHD VERSION

From build date 11.200

Climate Unit Stepper Motor Testing

t8008643.tif

This service bulletin is intended to give information on the Climate Unit Stepper MotorTesting procedure for the VN, VHD VERSION2 vehicles.

For further information, refer to other service information in group 8.

Contents: Stepper Motor page 3

Stepper Motor, Testing page 4

Note: Information is subject to change without notice.Illustrations are used for reference only and may differ slightly from the actualvehicle being serviced. However, key components addressed in this information arerepresented as accurately as possible.

PV776-20 001146 USA145

8/13/2019 PV776-20 001146

2/5

Volvo Trucks North America, Inc. Date Group No. Page

Service Bulletin 12.2003 870 15 2(5)

Special Tools

W2001014

J-39200 J-46315

Multimeter StepperMotor Test

Tool

8/13/2019 PV776-20 001146

3/5

Volvo Trucks North America, Inc. Date Group No. Pa

Service Bulletin 12.2003 870 15 3

Stepper Motor

t8008728.tif

1 Fresh Air/Recirculate

2 Air Distribution (Vents, Defrost, Floor, etc.)

3 Blend Air Mixing (ECC/MCC), mechanical heat

control valve (MCC)

Stepper motors are one of the many new components onthe front HVAC unit for VERSION2 vehicles. There arethree individual stepper motors located on the topside of

the front HVAC unit.

Stepper motors are used to control various doormovements within the climate unit for air distribution,temperature control and fresh air recirculation. Thesesmall devices convert electric signals to a steppedrotating motion that directly moves a door/flap accordingto selected HVAC function from the dash control panel.The stepper motor consists of a rotor with permanentmagnets, four coil windings and four in-series diodes.

8/13/2019 PV776-20 001146

4/5

Volvo Trucks North America, Inc. Date Group No. Page

Service Bulletin 12.2003 870 15 4(5)

Stepper Motor, TestingNote: Refer to the Cab Climate System, RepairInstructions Service Bulletin (Group 8) for furtherinformation.99

Note: For further information on Stepper Motor testingrefer toStepper Motor page 3

Measuring amperage, milliamps (mA)

J-46315 connected to stepper motor

J-39200 connected to red and black socket pinsof test tool

Note: Normal switch position and 1 - 4 are measurementsof the coils. Reversed switch position and 1 4 aremeasurements of the diodes.

1

W8003450

Set switches to "Normal" and "Position 1".

2Rotate the knob and note the measurement for eachposition 1 4.

3Repeat procedure for the "Reversed" switch position.

Note: Read the measurements in the chart and matchthe results from left to right. A good stepper motorcorresponds to the first row in the chart.

Note: : It is important to check the battery conditionof the tool before each test. A weak battery will causemeasurement errors (See "Battery Check"BatteryTesting page 5).

8/13/2019 PV776-20 001146

5/5

Volvo Trucks North America, Inc. Date Group No. Pa

Service Bulletin 12.2003 870 15 5

Stepper Motor Testing Chart

Normal, 1 4 Reversed, 1 4 Comment Action

10 14 mA < 0.2 mA Stepper Motor OK None

15 350 mA < 0.2 mA Shorted coil

< 0.2 mA < 0.2 mA Open coil or Open diode

19 24 mA 19 24 mA Shorted diode

0.3 9.9 mA < 0.2 mA *If battery in tester OK,stepper motor coil has highresistance.

Replace stepper motor

Note: If all readings taken with the DMM are less than0.2 mA, check the fuse in the DMM.

Battery TestingThe J-46315 uses one alkaline, 1.5V AA battery. Perforthe following test before using the stepper motor tester.

1 DMM set to read DC voltage.

2 J-46315, set switches to "Normal" and "Position 4".

3 Connect the red lead of the DMM to the red socket pof the J-46315.

4 Connect the black lead of the DMM to the rear side opin 6 (green wire) of the tester lead.

5 Measure the voltage of the AA battery. If the voltagebelow 1.5V DC, Replace the battery before performinany further tests.

Note: It is important to check the battery condition ofthe tool before each test. A weak battery will causemeasurement errors.